Autophagy consists of the sequestration of organelles and proteins in autophagic vesicles (AV) and degradation of this cargo through lysosomal fusion (1). Autophagy allows tumor cells to survive metabolic and therapeutic stresses (2-5). Multiple publications indicate therapy-induced autophagy is a key resistance mechanism to many anti-cancer agents. Chloroquine (CQ) derivatives block autophagy by inhibiting the lysosome (3,6,7). Based on these findings, clinical trials combining cancer therapies with hydroxychloroquine (HCQ), (which is safer than CQ to dose escalate) have been launched. Preliminary results indicate these combinations have activity (8-13), but it is still unclear if this activity is consistently due to the addition of HCQ. High micromolar concentrations of HCQ are required to inhibit autophagy. While there is some pharmacodynamic evidence of autophagy inhibition with HCQ in cancer patients, it is inconsistent because adequate concentrations are not achieved in all patients. There is an unmet need to develop more potent inhibitors of autophagy. The design and synthesis of dimeric analogs of CQ, that exploit the thermodynamic advantages imparted by polyvalency (14, 15), has been a subject of intensive study for over 10 years (16-18). An early report by Vennerstrom (17) described the synthesis of heteroalkane-bridged bisquinolines as potential antimalarials, but none of the compounds had sufficient antimalarial activity to warrant further investigation. Subsequently, Sergheraert (16) reported that tetraquinolines, i.e., dimers of bisquinolines, afforded potent antimalarials, confirming the possibility that the application of the polyvalency strategy could afford increased potency, at least with respect to antimalarial activity.
More recently, Lee (19) has described the potentiation of AKT inhibitors by fluorinated quinoline analogs. Solomon (20) has reported the preparation of “repositioned” chloroquine dimers, based on the use of a piperazine connector. These results suggest that these chloroquine analogs could serve as bases for the development of a new group of effective cancer chemotherapeutics. We have examined the application of the strategy of polyvalency (14, 15) to the synthesis of novel autophagy inhibitors by preparing a dimeric chloroquine (Lys01, FIG. 11 or 12), from commercially available materials. We have recently reported a series of BAIs that potently inhibit autophagy and impair tumor growth in vivo (21). The structural motifs that are necessary for improved autophagy inhibition compared to CQ include the presence of two aminoquinoline rings and a triamine linker, as shown in the lead compound, 1 (Lys 01) which is a 10-fold more potent autophagy inhibitor than HCQ. Compared to HCQ, Lys 05, a water soluble salt of Lys01, more potently accumulates within and deacidifies the lysosome, resulting in impaired autophagy and tumor growth. At the highest dose administered, some mice developed Paneth cell dysfunction that resembles the intestinal phenotype of mice and humans with genetic defects in the autophagy gene ATG16L1(22), providing in vivo evidence that Lys05 targets autophagy. Unlike HCQ, significant single agent antitumor activity is observed without toxicity in mice bearing xenograft tumors treated with lower doses of Lys05, establishing the therapeutic potential of this compound in cancer. However, while Lys05 is 10-fold more potent than HCQ in in vitro autophagy assays, it is cytotoxic only at micromolar concentrations in most cancer cells.
In the present invention, we demonstrate the preparation and the unexpected biological activity of asymmetric bisaminoquinolines and related compounds via changing the linker length and/or disrupting the symmetry of the previously employed linkers. We describe unexpected increase in anti-cancer properties and capacity for autophagy inhibition of bivalent aminoquinolines when linker length is changed substantially and/or asymmetrically from Lys01.